Railcars have undercarriage truck assemblies that include a frame, one or more wheel assemblies, and roller bearings that connect the wheel assemblies to the frame. Each wheel assembly includes an axle with journals at opposite ends thereof and wheels connected to the axle. Each roller bearing includes a first component mounted to the journal that turns with the journal and a second component that is mounted to the frame.
Various types of roller bearings are used for railcars. One type of roller bearing is a tapered roller bearing that includes one or more rows of tapered rollers. Tapered roller bearings, and other types of bearings, include a lubricant within the bearing to reduce resistance to movement between components of the bearing. Bearings may also include a seal to contain the lubricant within the bearing and to prevent water, dirt, and debris from entering the bearing.
One prior seal for a tapered roller bearing includes a seal case mounted to a bearing cup of the tapered roller bearing. The seal further includes an insert press-fit in the seal case, a rotor mounted to a journal, and a slinger connected to the rotor. During operation of the tapered roller bearing, the rotor and slinger rotate together relative to the seal case and insert as the journal turns. Further, the assembly of the seal case, insert, rotor, and slinger defines a labyrinth seal that resists egress of lubricant from the tapered roller bearing and the ingress of water and debris into the bearing.
The seal may be separately manufactured from the rest of the tapered roller bearing. In one prior approach, the seal case, insert, rotor, and slinger are assembled at a first facility, transported to a second facility, and then subsequently assembled with a bearing cup and a wear ring of the tapered roller bearing at the second facility. More specifically, the seal case and insert are assembled at the first facility by pressing the insert into the seal case. Next, the rotor is press-fit into the insert which fixes the rotor to the insert. The press-fit engagement between the rotor and the insert keeps the rotor assembled with the seal case and insert during transport. An annular inner wall of the slinger is then inserted into an opening of a slightly larger annular wall of the rotor to form a slip-fit connection therebetween. There is some nominal interference between the annular walls of the slinger and the rotor, but the slinger can shift relative to the rotor. The slinger may be made of a more pliable material than the rotor and the loose fit between the slinger and rotor permits the slinger to expand more than the rotor when the rotor/slinger assembly is subsequently press fit onto a wear ring. The assembled seal including the seal case, insert, rotor, and slinger is packaged at the first facility and transported to the second facility.
After the seal has been transported from the first facility to the second facility, an operator at the second facility removes the seal from the package. The operator inserts the seal into a press machine and operates the press machine to press a wear ring into the slinger of the seal which expands the annular wall of the slinger into tight engagement with the annular wall of the rotor and inhibits relative rotary and axial movement between the rotor and slinger. The pressing of the wear ring into the slinger also shifts the rotor axially relative to the insert and disengages the press-fit engagement between the rotor and the insert which disconnects the rotor/slinger assembly from the insert/seal case assembly. Thus, the operation of press-fitting the wear ring into the slinger both secures the wear ring to the rotor/slinger assembly and disengages the rotor/slinger assembly from the insert/seal case assembly. This disconnecting operation permits the rotor/slinger assembly to turn relative to the insert/seal case assembly with turning of the journal. Although the disconnecting operation is necessary in the prior approach to permit the rotor/slinger assembly to turn, the disconnecting operation complicates assembly of the tapered roller bearing at the second facility.
Further, the rotor and the insert are made from an injection-molded plastic and the tolerances between the rotor and the insert may be too loose or too tight which adversely affects assembly and transportation of the seal. For example, if the rotor is too loosely engaged with the insert, the slip-fit connection between the rotor and the insert may permit the rotor and the slinger to fall off of the insert/seal case assembly when the seal is removed from the package at the second facility. If the rotor is too tightly engaged with the insert, the operation of press-fitting the wear ring into the slinger may cause the rotor to rip the insert out of the seal case.